Door position sensor for an electromagnetic door lock

ABSTRACT

A door position sensor of an electromagnetic door lock. The electromagnetic lock also includes an electromagnet and a strike plate. The electromagnet is secured to the door frame and the strike plate is movably mounted to the door so that a controlled amount of door movement in the opening direction is permitted while the strike plate remains in contact with an energized electromagnet. The door position sensor may comprise a sensor in or on the electromagnet and a permanent magnet mounted to the door and disposed in proximity to the sensor when the door is in a closed position. The sensor may be a reed switch or a Hall Effect sensor. The permanent magnet and strike plate may be mounted to the door by a mounting tray. The mounting tray may include indicia to aid in providing a proper alignment of the strike plate to the door and electromagnet.

The present application claims the benefit of U.S. Provisional PatentApplication No. 62/322,344, filed Apr. 14, 2016 and U.S. ProvisionalPatent Application No. 62/381,387, filed Aug. 30, 2016, the contents ofwhich are incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a door position sensor of anelectromagnetic door lock wherein the electromagnetic door lock securesa door to a door frame in a closed position. The electromagnetic lockalso includes an electromagnet and a strike plate. The electromagnet issecured to the door frame and the strike plate is movably mounted to thedoor so that a controlled amount of door movement in the openingdirection is permitted while the strike plate remains in contact with anenergized electromagnet. The door position sensor may comprise a sensorin or on the electromagnet and a permanent magnet mounted to the doorand disposed in proximity to the sensor when the door is in a closedposition. The sensor may be a reed switch or a Hall Effect sensor,whereby the sensor monitors initial door movement away from the doorframe. In one aspect of the invention, the permanent magnet and movablymounted strike plate may be mounted to the door by way of a mountingtray. The mounting tray may include indicia to aid in providing a properalignment of the strike plate to the door and electromagnet. In the caseof an electromagnetic door lock equipped with an Eco-Mag design feature,the door position sensor may be used to determine whether additionalpower should be provided to the electromagnet to secure the lock in alocked state and prevent unwanted opening of the door. The door positionsensor may also be used in conjunction with an electromagnetic door lockhaving a De-Mag design feature to determine when a “delay period” shouldbe initiated.

BACKGROUND OF THE INVENTION

Electromagnetic door locks are widely used in diverse electronic doorapplications. These locks typically use electromagnets attached to thedoor frame in conjunction with a ferromagnetic strike plate attached tothe door, to hold the door firmly closed. When the electromagnet isenergized and is in contact with the strike plate, the strike platebecomes an armature for the electromagnet, thus providing a mechanismfor locking the door to the frame.

In current designs such as disclosed in U.S. Pat. No. 5,758,913, meansare provided in the electromagnetic door lock to permit a controlledamount of door movement in the opening direction while the armature orstrike plate of the lock remains in contact with an energizedelectromagnet, to improve the ability of a door equipped with anelectromagnetic lock to withstand a physical blow. This design featureof the electromagnetic door lock is referred to herein as an “EnergyAbsorbing” design feature. A coil spring allows for some relativemovement between the door and strike plate. The coil spring provideslinear elasticity to the door by absorbing some of the kinetic energy ofthe blow upon compression of the spring, thus lowering the peak forceexperienced to separate the strike plate from the armature during aphysical attack against the door and allowing for a lower poweredelectromagnet to be used.

In other current electromagnetic door lock designs, there may also exista means that momentarily delays de-energizing of the electromagnet aftera force to open the door is applied. The application of an opening forceis detected by sensing when initial door movement away from the doorframe is detected using a suitable door position sensor. This designfeature is often associated with exit doors in commercial buildings orrestaurants that permit emergency egress through doors normally locked.In a delayed electromagnetic door lock (“De-Mag” design feature), if anopening force is applied to a locked door continuously through a firstpredetermined period of time (the “delay period”), the electromagnetwill be de-energized, allowing the door to be opened. If the openingforce applied to the door is terminated within a second predeterminedperiod of time (the “nuisance delay period”) wherein the secondpredetermined period of time is less than the first predetermined periodof time, the electromagnet will remain energized and the door willremain locked. Typically, an audible signal will be sounded when initialdoor movement is detected providing an alarm that an attempt is beingmade to exit through the locked door.

In still other current electromagnetic door lock designs, there mayexist a power savings design feature (Eco-Mag design feature). By theEco-Mag design feature, the electromagnet has a resting state whereinonly enough power is supplied to the electromagnet to keep the door in alocked state when subjected to only environmental stimuli, such as agust of wind. Then, should a more forceful attempt be made to open thedoor (i.e., an unauthorized attempt to enter/exit), power to theelectromagnet is increased to keep the door locked against theunauthorized attempt to open the door. The Eco-Mag design feature alsorequires the use of a suitable door position sensor to detect when acontrolled amount of initial door movement in the door-opening directionhas occurred, thereby sensing when an unauthorized attempt to enter isbeing made.

Door position sensors used in conjunction with De-Mag or Eco-Mag designsmay generally be comprised of at least one permanent magnet connected tothe strike plate and a sensor mounted within the electromagnet, whereinthe sensor is responsive to initial movement of the strike plate awayfrom the electromagnet.

Door position sensors of the above type, when used in conjunction withelectromagnetic door locks having means to permit a controlled amount ofdoor movement in the opening direction while the strike plate remains incontact with an energized electromagnet, require an excessive amount ofdoor movement in the opening direction before a “door-opening” conditionis signaled. This is because the coil spring needed to provide acontrolled amount of door movement must first be compressed a givendistance, then the strike plate must begin to move away from theelectromagnet before the “door-opening signal is generated. Thisexcessive amount of door movement is undesirable because the excessivemovement creates a false impression to the user that the door is notentirely secured.

What is needed in the art is a door position sensor used in conjunctionwith an electromagnetic door lock that senses initial movement of thedoor away from the door frame and not movement of the strike plate awayfrom the electromagnet, thereby providing a more sensitive and robustway of detecting initial door movement in De-Mag or Eco-Magarchitectures.

What is also needed is a door position sensor that can detect initialmovement of the door away from the door frame within about ⅛ inch ofmovement.

What is needed further in the art is a strike plate mountable to a traywherein the at least one magnet of a door position sensor is containedby the tray, thereby providing for a more compact and convenient packagethat may be used in with De-Mag and Eco-Mag architectures.

It is the principal object of the present invention to provide this andother needs.

SUMMARY OF THE INVENTION

Briefly described, the present invention is directed toward a doorposition sensor for use in conjunction with an electromagnetic door lockfor securing a door to a door frame, wherein the electromagnetic doorlock includes a strike plate assembly and an electromagnet and wherein astrike plate of the strike plate assembly is magnetically held incontact with the electromagnet when the electromagnet is energized tosecure the door to the door frame. The door position sensor includes asensor connectable to the door frame, and a permanent magnet fixablyconnectable to the door, wherein movement of the door away from the doorframe is detected by the door position sensor while the strike plate isheld in contact with the electromagnet.

The sensor may be a Hall Effect sensor or a reed switch. The sensor maybe on or in the electromagnet.

With the aforementioned door position sensor, movement of the door awayfrom the door frame may be less than about ¾ inches. In one aspect ofthe invention, movement of the door away from the door frame is withinthe first ⅛ inches of door movement away from the door frame.

The door position sensor may also include a second permanent magnetfixably connected to the door with a second sensor connectable to thedoor frame to form a second door position sensor, wherein movement ofthe door away from the door frame is detected by at least one of thedoor position sensors while the strike plate is held in contact with theelectromagnet.

The door position sensor may further include a strike tray having acavity defined by the strike tray and fixably connectable to the door,wherein the permanent magnet is integrally mounted to the strike trayand wherein the cavity is proportioned to receive the strike plate.Further, a second permanent magnet may be integrally mounted to thestrike tray with a second sensor connectable to the door frame to form asecond door position sensor, and wherein movement of the door away fromthe door frame is detected by at least one of the door position sensorswhile the strike plate is held in contact with the electromagnet.

The aforementioned strike tray may also include indicia to aid in theproper positioning of the strike plate relative to the electromagnet.The strike tray of the door position sensor may also include a wallwherein when the strike plate is received in the cavity, the strikeplate abuts the wall to align the strike plate with the electromagnet.In a further aspect of the invention, the cavity may be defined by atleast one wall or at least one edge for receiving the strike plate.

In a further aspect of the invention, an electromagnetic door lock isprovided for selectively locking and unlocking a door to a door framewhere the door is pivotally coupled to the door frame. Further, theelectromagnetic lock includes an electromagnet mountable to the doorframe and a strike plate configured to be mounted to the door. Stillfurther, the electromagnetic door lock includes a door position sensorhaving a permanent magnet fixably connectable to the door and a sensoron or in the electromagnet, wherein movement of the door away from thedoor frame is detected by the door position sensor while the strikeplate is held in contact with the electromagnet when energized.

The sensor of the aforementioned electromagnetic door lock may be a HallEffect sensor or a reed switch.

Still further, with the aforementioned electromagnetic door lock,movement of the door away from the door frame is less than about ¾inches. In a further aspect of the invention, movement of the door awayfrom the door frame is within the first ⅛ inches of door movement awayfrom the door frame.

Further the door position sensor of the aforementioned electromagneticdoor lock may include a second permanent magnet fixably connected to thedoor and a second sensor on or in the electromagnet to form a seconddoor position sensor, wherein movement of the door away from the doorframe is detected by at least one of the door position sensors while thestrike plate is held in contact with the electromagnet.

The door position sensor of the aforementioned electromagnetic door lockmay further include a strike tray having a cavity defined by the striketray, wherein the strike tray is fixably connectable to the door,wherein the permanent magnet is integrally mounted to the strike trayand wherein the cavity is proportioned to receive the strike plate.Further, a second permanent magnet may be integrally mounted to thestrike tray and a second sensor may be connectable to the door frame toform a second door position sensor, wherein movement of the door awayfrom the door frame is detected by at least one of the door positionsensors while the strike plate is held in contact with theelectromagnet.

Further, the aforementioned strike tray may include indicia to aid inthe proper positioning of the strike plate relative to theelectromagnet. Also, the strike tray may include a wall wherein when thestrike plate is received in the cavity, the strike plate abuts the wallto align the strike plate with the electromagnet. Further, theaforementioned cavity may be defined by at least one wall or at leastone edge for receiving the strike plate.

Numerous applications, some of which are exemplarily described below,may be implemented using the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a typical electromagnetic door lock installation;

FIG. 2 is a plan view of an electromagnetic door lock, including astrike plate and permanent magnets connected to sides of the strikeplate as in the prior art;

FIG. 3 is a plan view of a mounting bracket for the electromagnet and atemplate used in mounting the strike plate to a door as in the priorart;

FIG. 4 is an exploded perspective view of the strike plate with the atleast one permanent magnet connected to the strike plate and the strikeplate mounting bolt assembly used to movably mount the strike plate tothe door;

FIG. 5 is an exploded perspective view of the strike plate in accordancewith the invention with one of the associated permanent magnetsseparately mountable/mounted to the door;

FIG. 5A is a schematic drawing of an electromagnetic door lock in adoor-closed position in accordance with the invention;

FIG. 5B is a schematic drawing of the electromagnetic door lock shown inFIG. 5A with the door opened a first distance without separation of thearmature from the electromagnet in accordance with the invention; and

FIGS. 6 and 6A are exploded perspective views of a strike plate and trayassembly in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a typical electronic door lock installation. In a typicalinstallation, an electromagnet 12 is secured to a door frame 14. Aferromagnetic armature or strike plate 16 is mounted on front face 33 ofdoor 18. When door 18 is closed and electromagnet 12 is energized,electromagnet 12 exerts a magnetic force against strike plate 16 to holddoor 18 in a closed and magnetically locked position.

FIGS. 2 through 4 show electromagnetic lock 20 comprised generally of anelectromagnet 12 and strike assembly 22 which includes strike plate 16and permanent magnets 62 connected to ends of strike plate 16. A priorart door position sensor 32 as shown as shown in FIG. 2 includespermanent magnet 62 connected to strike plate 16 and sensor 65 on or inelectromagnet 12 wherein magnet 62 is disposed in proximity to sensor 65when the door is closed. With reference to FIG. 3, as disclosed incommonly owned U.S. Patent Publication No. 2013/0127260, electromagnet12 may be mounted onto a door frame 14 via electromagnet mountingbracket 26 or other mounting means. A template 28 may be mounted to door18 and keyed to reference mounting bracket 26 so as to indicate properplacement and hole sizes and depths for drilling pilot holes 30 used inmounting strike plate. Permanent magnet 62 is used to sense theproximity of strike plate 16 to electromagnet 12 and, in conjunctionwith sensor 65 in or on the electromagnet, form door position sensor 32.Note that, since the permanent magnet 62 is connected directly to thestrike plate, door position sensor 32 of the prior art detects only themovement of magnet 62, and therefore strike plate 16, away fromelectromagnet 12. Sensor 32 does not sense initial movement of the dooraway from the door frame while the strike plate remains in contact withan energized electromagnet.

Turning further to FIG. 4, an exploded view of the device described inreference to FIG. 2 is shown. Included in FIG. 4 is strike assembly 22,including strike plate 16 and permanent magnets 62 connected to ends ofstrike plate 16. FIG. 4 also depicts an exploded view of strike platestrike plate mounting bolt assembly for movably mounting the strikeplate to the door, as disclosed in commonly owned U.S. ProvisionalApplication Ser. No. 62/322,344, hereby incorporated by reference.Strike assembly 22 including strike plate 16 and one or more permanentmagnets 62, is movably mounted to door 18 via strike plate mounting boltassembly 34. One or more flexible washers 36 may be included to allowstrike plate 16 to move, to a degree, so that strike plate 16 can abutthe electromagnet in full contact for maximum hold force when door 18 isshut and the electromagnet is energized. Guide pins 38 are mounted inholes 31 in the door whereby pins 38 may slideably mate withcorresponding holes in the strike plate (not shown) so as to keep thestrike plate in proper alignment with the door through the strikeplate's movement relative to the door. Strike plate mounting boltassembly 34 may include a bolt (see e.g., bolt 40 in FIG. 6A), post 42and a resilient member 44. In one aspect of the invention, resilientmember 44 is a Belleville washer assembly composed of at least oneBelleville washer. As seen in FIG. 6A, bolt 40 may include a flange orhead 46 which abuts the rear face 48 of door 18 (see FIG. 1), and ashaft 50. Through bore 30′, formed in door 18, is sized to receive anouter diameter of shaft 50. Head 46 of bolt 40 may be configured to betamper-resistant from its exposed end.

Returning to FIG. 4, post 42 includes head end 52 and shaft end 54wherein the head end is larger in diameter than the shaft end. Malethreads formed in shaft end 54 are configured for engagement with femalethreads in bolt 40. Strike plate 16 includes first bore 56 and secondbore 58 larger in diameter than first bore 56. First bore 56 is sized toloosely receive shaft end 54 of post 42. Second bore 58 forms a cavityfor receiving resilient member 44 which may be comprised of one moreindividual Belleville washers. Each Belleville washer may be dimensionedto have an outer diameter smaller than a diameter of second bore 58 anda center hole larger in diameter than the outer diameter of shaft end 54of post 42.

To complete the assembly of the strike plate to the door, bolt 40 isinserted into through bore 30′ defined within door 18. After insertingthe shaft end 54 of post 42 through each bore of the at least oneBelleville washers, shaft end 54 is inserted through first and secondbores 56, 58 of strike plate 16. Male threads on shaft end 54 are thenthreaded into female threads within bolt 40. Post 42 is then tightenedinto bolt 40 until opposing surfaces of the at least one Bellevillewasher are in contact with second bore surface 58 and the underside ofhead end 52 of post 42 and, preferable, until post head end 52 is flushor below the outer surface of the strike plate 16.

As described in commonly owned U.S. Provisional Application Ser. No.62/322,344, selective stacking of two or more Belleville washers(Belleville washer assembly 44) may be utilized to tune theforce/deflection characteristics needed for the particular application.As is known in the art, a single Belleville washer is generally conicalin cross-section and exhibits certain load/deflection characteristicsbased upon its thickness, material, shape, etc. When two washers arestacked so that their convex surfaces are facing in the same direction,the force (load) doubles with no increase in deflection. When twowashers are stacked so that their convex surfaces are facing in oppositedirections, deflection is doubled with no increase in force (load).Thus, by selecting the number of washers and the relative orientationsof the selected washers, the force/deflection characteristic of thecollection of Belleville washers can be varied to suit the application.

With reference to FIGS. 5, 5A and 5B, and in accordance with theinvention, one or more permanent magnets 62′ is fixedly mounted directlyto door 18 by fasteners 63 inserted into holes 67. (In reference to FIG.5, one magnet (left side) is shown for mounting to the door and theright side magnet is already mounted to door 18). Each one or moremagnets 62′ is positioned so as to correspond to and magnetically engagewith a respective sensor 65 housed within electromagnet 12 when door 18is in the fully closed position, thereby forming a door position sensor.By way of example, electromagnet 12 may include one or more reedswitches 65 a as sensors, in or on the electromagnet, in the vicinityshown as X in FIG. 2, and excited by a respective permanent magnet 62′.The one or more sensors may have a first operating condition (i.e. openor closed contacts in the exemplar reed switch) when door 18 is fullyclosed as shown in FIG. 5A. As the door is opened while strike plate 116remains in contact with the electromagnet (FIG. 5B), one or more magnets62′ no longer bear upon the sensor causing the sensor to toggle to theopposing second operating condition (i.e. the open contacts are nowclosed or vice versa). The operating condition status of the sensor maybe monitored by software operating in conjunction with electromagneticlock 20, or by software provided by the user in the field, so as tosense the position of door 18 relative to door frame 14. It should benoted that, because one or more magnets 62′ are fixedly mounted to door18, door 18 may be opened a first distance—shown as D₁ minus D in FIGS.5A and 5B (such as less than about ¾ inches)—due to initial compressionof Belleville washer assembly 44 before strike assembly 22 begins tomove away from electromagnet 12. The initial movement causes sensor 65,such as reed switch 65 a, to toggle and to cause the software to sensean opened door state while the strike plate remains in contact with theenergized electromagnet. Thus, a door-opening signal is triggered muchearlier than if triggered by initial movement of the strike plate awayfrom the electromagnet.

In the case of an electromagnetic door lock having the De-Mag designfeature, compression of Belleville washer assembly 44 allows door 18 tomove away from door frame 14 to thereby allow the delay function of thelock to operate. In the case of an electromagnetic door lock having anEco-Mag design feature, compression of the Belleville washer assembly 44allows the lock circuitry time to sense an initial unauthorized movementof the door away from the door frame (i.e., movement of the door withoutreceipt of proper credentials) and to then provide full power to theelectromagnet to keep the door in its locked state.

The one or more reed switches 65 a discussed above may be replaced withone or more Hall Effect sensors 65 b to provide greater sensitivity fordetecting initial door movement away from the door frame in an openingdirection which may be required by the Eco-Mag design feature. Withgreater sensitivity, a Hall Effect sensor may be capable of detectinginitial door movement away from the door frame of as little as about ⅛inch, as measured between the face of the electromagnet and theassociated permanent magnet. Thus, in the case of an electromagneticdoor lock having an Eco-Mag design feature, within the first ⅛ inch ofdoor movement in the opening direction, if an unauthorized attempt toopen the door is detected (the door is moved in an opening directionwithout proper credentials) the circuitry of the electromagnetic doorlock will receive a signal from the Hall Effect sensor and provide fullpower to the electromagnet to prevent the door from being openedfurther.

Turning now to FIGS. 6 and 6A, in accordance with a further aspect ofthe invention, exploded views of a strike assembly 122 are shown. Again,a complementary electromagnet (such as electromagnet 12 shown in FIG.2), with suitable sensor 65, 65 a, 65 b as described above, is mountedto door frame 14 as known in the art. Strike assembly 122 is generallycomprised of a strike plate 116, strike tray 124 and at least onepermanent magnet 162 integrally connected to tray 124. Strike tray 124has a back panel 125 and walls 126, 127. Opposing side edges 128, 129abut permanent magnets 162, respectively. Walls 126, 127 and side edges128, 129 define a cavity 131 which is proportioned to receive strikeplate 116. Strike tray 124 includes a plurality of holes 130 configuredto receive fasteners 132 for fixedly mounted strike tray 124 to frontface 32 of door 18. As shown in FIG. 6, to properly position and orientstrike tray 124, and to provide the location for pilots holes 130′within door 18 which correspond to mounting holes 130 on strike tray124, back panel 125 of strike tray 124 may include template indicia 133keyed to reference mounting hole locations of bracket 26.

Strike plate 116 may be movably mounted to door 18 and within striketray 124 via strike plate mounting bolt assembly 34, as described above.It should be noted that guide pins 38 (see FIG. 4) and correspondingholes in the strike plate and door are no longer necessary. Inaccordance with the invention, strike plate 116 slideably resides withincavity 128 where at one or more of walls 126, 127 and side edges 128,129 have a sufficient thickness to abut a side surface 150 of strikeplate 116 such that strike plate 116 may remain within cavity 131 and inproper alignment with the door through the strike plate's movementrelative to the door. This allows the body of the face plate to beunimpeded, without any holes needed to receive the guide pins.Therefore, with the greater mass due to the absence of guide pin holes,the holding force exerted on the ferromagnetic strike plate by theenergized electromagnet is enhanced.

As described above, strike plate mounting bolt assembly 34 may includebolt 40, post 42 and a Belleville washer assembly 44 composed of atleast one Belleville washer as described above. As seen in FIG. 6A, bolt40 may include a flange or head 46 which abuts the rear face 48 of door18 (see FIG. 1), and a shaft 50. Through bore 130″ formed in door 18 andhole 134 in tray 124 are sized to receive an outer diameter of shaft 50.Head 46 of bolt 40 may be configured to be tamper-resistant from itsexposed end.

As described above, post 42 includes head end 52 and shaft end 54wherein the head end is larger in diameter than the shaft end. Malethreads formed in shaft end 54 are configured for engagement with femalethreads in bolt 40. Strike plate 116 includes first bore 156 and secondbore 158 larger in diameter than first bore 156. First bore 156 is sizedto loosely receive shaft end 54 of post 42. Second bore 158 forms acavity for receiving Belleville washer assembly 44 which may becomprised of one more individual Belleville washers. Each Bellevillewasher may be dimensioned to have an outer diameter smaller than adiameter of second bore 58 and a center hole larger in diameter than theouter diameter of shaft end 54 of post 42.

To complete the assembly of strike assembly 122 to door 18, strike tray124 (with attached permanent magnet(s)) is first aligned with andsecured to door 18. Then, bolt 40 is inserted into through bore 130″defined within door 18 and hole 134 in strike tray 124. After insertingthe shaft end 54 of post 42 through each bore of the at least oneBelleville washers, shaft end 54 is inserted through first and secondbores 56, 58 of strike plate 116. Male threads on shaft end 54 are thenthreaded into female threads within bolt 40. Post 42 is then tightenedinto bolt 40 until opposing surfaces of the at least one Bellevillewasher are in contact with second bore surface 58 and the underside ofhead end 52 of post 42 and, preferable, until post head end 52 is flushor below the outer surface of the strike plate 116.

Strike tray 124 may include at least one permanent magnet 162 fixedlymounted thereon, as described above. Sensor 65 may include a Hall Effectsensor 65 b positioned to be excited by magnet 162 when door 18 is inthe fully closed position. Complementary electromagnet may alternativelyinclude a reed switch 65 a to be excited by the at least one permanentmagnet 162. In the case where a permanent magnet is disposed adjacenteach side wall 128, 129 of strike tray 124, any combination of reedswitches/Hall Effect sensors may be incorporated in the complementaryelectromagnet, making the strike assembly 122 flexibly adaptable to amultitude of electromagnetic lock assemblies found in the field. Forexample, a first permanent magnet may be used in cooperation with a HallEffect sensor to operate an Eco-Mag design feature while a secondpermanent magnet may be used in conjunction with a reed switch tooperate a De-Mag design feature or to work in conjunction with anothertype of field-selected circuitry in need of sensing the initial movementof a door.

In FIGS. 5, 5A, 5B and 6, the “one or more” permanent magnets 62′ areshown as two permanent magnets, both being fixably connectable to thedoor. It is understood that the invention disclosed herein alsocomprehends one permanent magnet being fixably connectable to the doorand a second permanent magnet being fixably connectable to an end of thestrike plate.

Although the present invention has thus been described in detail withregard to the preferred embodiments and drawings thereof, it should beapparent to those skilled in the art that various adaptations andmodifications of the present invention may be accomplished withoutdeparting from the spirit and the scope of the invention. Accordingly,it is to be understood that the detailed description and theaccompanying drawings as set forth hereinabove are not intended to limitthe breadth of the present invention, which should be inferred only fromthe following claims and their appropriately construed legalequivalents.

1. A door position sensor for use in conjunction with an electromagneticdoor lock for securing a door to a door frame, wherein theelectromagnetic door lock includes a strike plate assembly and anelectromagnet and wherein a strike plate of said strike plate assemblyis magnetically held in contact with said electromagnet when saidelectromagnet is energized to secure said door to said door frame, saiddoor position sensor comprising: a) a sensor connectable to said doorframe; and b) a permanent magnet fixably connectable to said door,wherein movement of said door away from said door frame is detected bysaid door position sensor while said strike plate is held in contactwith said electromagnet.
 2. The door position sensor of claim 1 whereinsaid sensor is a Hall Effect sensor or a reed switch.
 3. The doorposition sensor of claim 1 wherein said movement of said door away fromsaid door frame is less than about ¾ inches.
 4. The door position sensorof claim 1 wherein said movement of said door away from said door frameis within the first ⅛ inches of door movement away from said door frame.5. The door position sensor of claim 1 wherein said sensor is on or insaid electromagnet.
 6. The door position sensor of claim 1 wherein asecond permanent magnet is fixably connected to said door, a secondsensor is connectable to said door frame to form a second door positionsensor, and wherein movement of said door away from said door frame isdetected by at least one of said door position sensors while said strikeplate is held in contact with said electromagnet.
 7. The door positionsensor of claim 1 further including a strike tray having a cavitydefined by said strike tray and fixably connectable to said door,wherein said permanent magnet is integrally mounted to said strike trayand wherein said cavity is proportioned to receive said strike plate. 8.The door position sensor of claim 7 wherein a second permanent magnet isintegrally mounted to said strike tray and a second sensor isconnectable to said door frame to form a second door position sensor,and wherein movement of said door away from said door frame is detectedby at least one of said door position sensors while said strike plate isheld in contact with said electromagnet.
 9. The door position sensor ofclaim 7 wherein said strike tray includes indicia to aid in the properpositioning of the strike plate relative to the electromagnet.
 10. Thedoor position sensor of claim 7 wherein said strike tray includes a walland wherein when said strike plate is received in said cavity, saidstrike plate abuts said wall to align said strike plate with theelectromagnet.
 11. The door position sensor of claim 10 wherein saidcavity is defined by at least one wall or at least one edge forreceiving said strike plate.
 12. An electromagnetic door lock forselectively locking and unlocking a door to a door frame, the door beingpivotally coupled to the door frame, the electromagnetic lockcomprising: a. an electromagnet mountable to the door frame; b. a strikeplate configured to be mounted to the door; c. a door position sensorcomprising a permanent magnet fixably connectable to said door and asensor on or in said electromagnet, wherein movement of said door awayfrom said door frame is detected by said door position sensor while saidstrike plate is held in contact with said electromagnet when energized.13. The electromagnetic door lock of claim 12 wherein said sensor is aHall Effect sensor or a reed switch.
 14. The electromagnetic door lockof claim 12 wherein said movement of said door away from said door frameis less than about ¾ inches.
 15. The electromagnetic door lock of claim12 wherein said movement of said door away from said door frame iswithin the first ½ inches of door movement away from said door frame.16. The door position sensor of claim 12 wherein a second permanentmagnet is fixably connected to said door, a second sensor is on or insaid electromagnet to form a second door position sensor, and whereinmovement of said door away from said door frame is detected by at leastone of said door position sensors while said strike plate is held incontact with said electromagnet.
 17. The door position sensor of claim12 further including a strike tray having a cavity defined by saidstrike tray and fixably connectable to said door, wherein said permanentmagnet is integrally mounted to said strike tray and wherein said cavityis proportioned to receive said strike plate.
 18. The door positionsensor of claim 17 wherein a second permanent magnet is integrallymounted to said strike tray and a second sensor is connectable to saiddoor frame to form a second door position sensor, and wherein movementof said door away from said door frame is detected by at least one ofsaid door position sensors while said strike plate is held in contactwith said electromagnet.
 19. The door position sensor of claim 17wherein said strike tray includes indicia to aid in the properpositioning of the strike plate relative to the electromagnet.
 20. Thedoor position sensor of claim 17 wherein said strike tray includes awall and wherein when said strike plate is received in said cavity, saidstrike plate abuts said wall to align said strike plate with theelectromagnet.
 21. The door position sensor of claim 20 wherein saidcavity is defined by at least one wall or at least one edge forreceiving said strike plate.